Hem II Chapter 14 Part 1 2016

7/24/2019 Hem II Chapter 14 Part 1 2016

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Leukocytes: The Granulocytic and

Monocytic Series

Part I


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Learning objectives:

Upon completion of this lecture series the learner should

be able to competently discuss:

The differentiation and maturation of the granulocyte cell

series in detail

The differentiation and maturation of the monocyte-

macrophage cell series in detail

The function of granulocytes and monocytes

Methods of assessment of granulocytes and monocytes in

a clinical setting (absolute counts, differential counts,

morphology, staining patterns, etc.)

Chapter 14

The Leukocytes


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Part I: Granulocytes

Development and proliferation passes through 3 major phases in 3

different sites:

Phases

1. Proliferative phase:for cell number to increase and for

cells to start to differentiate

2. Maturation-storingphase: cells complete their maturation

and replenish the constantly changing reservoir in the BMstorage compartment.

3. Distribution / release to circulationthen to final

destination depending on demand which changes; infection

and tissue injury increases demand.

Sites

- Proliferative compartment of BM

- Maturation/storing compartment of BM

- Circulation & the endothelium of the vascular system)


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Journey of a leukocyte


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Proliferative phase

Occurs in the proliferative compartment (mitotic pool) of BM which

houses cells capable of DNA synthesis & mitosis 4 stages:

Myeloblast: blastdenotes enlarged cells undergoing proliferation; representthe first cell that is morphologically recognizable as a granulocyte (granulation,

N/C ratio, chromatin pattern [clumped vs. dispersed], shape of nucleus, etc.)

Promyelocyte

Myelocyte

Metamyelocyte


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Maturation-storing phase:

Within this compartment metamyelocytes coming from

proliferative compartment make up to 45% of cells

Mature into band neutrophils (35%) [band describes the shape

of the nucleus in such cells

Further develops into segmented neutrophils (20%)

[segmented pertains to shape of nucleus as well].

Note that same phases apply to basophils, eosinophils and

monocyets.


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Band vs. segmented neutrophil

Band neutrophil in

peripheral blood film

Segmented neutrophil in

peripheral blood film
http://localhost/upload.wikimedia.org/wikipedia/commons/0/09/Neutrophils.jpghttp://localhost/upload.wikimedia.org/wikipedia/commons/0/0e/Band_neutrophil.JPG


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Distribution / Release to circulation:

Under the influence of various profiles of interleukins&

concurrent with the expression of homing markers(various

members of the selectin and integrin families like VCAM, ICAM, L-

selectin, LFA-1, etc) on vascular endothelium, mature

granulocytes start rolling towards sinusoid walls of BM into

circulation.

Granulocyte movement is also enhanced by cellular changes

decrease in size, N/C decrease, increased flexibility.

In the vascular system cells either stay in circulationor gather at

marginatingpools.

Marginating granulocytes adhere to the endothelim of blood

vessels; can be released on demand.

If needed as phagocytes (e.g. tissue injury), granulocytes (mainly

neutrophils) exit circulation to tissues by diapedesis.See next slide


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Developmental pathways of granulocytes & monocytes


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Maturation of Neutrophils1. Myeloblast

Earliest neutrophil precursor

Size: 10-18 mN:C ratio: High(4:1)

Nucleus: Oval or round

Chromatin: delicate, lacy, evenly stained

Nucleoli: 3-5

Cytoplasm: small rim of basophilic cytoplasmthat lacks granules.

Golgi apparatus: unstained area adjacent tonucleus

CD markers: CD33 and CD38.

Auer rods : which are aggregates of fused

lysosomes, may appear as red, needle-like

crystalline cytoplasmic inclusions.

These inclusions may appear alone or in

groups


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Maturation of Neutrophils

2. Promyelocyte

Size: larger than blast (14-20 m)

N:C ratio: High(3:1)

Nucleus: large, Oval or round

Chromatin: Coarser than blasts, lacy, purple-blue

Nucleoli: less prominent or absent

Cytoplasm: pale grayish blue.

Granules: Large blue purple primary granules (azurophilic

granules that contain loads of AMPs = antimicrobial

peptides(myeloperoxidase and chloroacetate esterase.

M t ti f N t hil


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3. Myelocyte

(The last stage that is capable

of division within BM)

Size: 12 to 18 m

N:C ratio: Decreased(2:1-1:1)

Nucleus: has a more oval appearance thanin previous stages

Chromatin: More condensed than blasts

Nucleoli: Usually absent

Cytoplasm: Light pink, with blue batches

Granules: Secondarygranules (specific): small, pink red to

pink violet in color.

The separate cell types: neutrophils, eosinophils, and

basophilsbecome visibly recognizable at this stage.


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4. MetamyelocyteSize: 10 to 18 m

N:C ratio: Decreased

Nucleus: Kidney-bean shaped

Chromatin: coarse, clumped, stains dark purple

Nucleoli: Not visible

Cytoplasm: Neutral pink

Granules: Predominance of

small pinkish red specific granules


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5. Band Neutrophil

(also called stab neutrophil,

and may normally present

in peripheral blood).

Size: 10 to 16 m

N:C ratio: Decreased (1:1)

Nucleus: More indented than

metamyelocyte

Horseshoe shape

Chromatin: pyknotic (condensed) at either end

of nucleus, Stain dark purple

Cytoplasm: Pink

Granules:Abundant small pinkish red specific granules


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6. Segmented Neutrophil

(Polymorphonuclear)Size: 10 to 16 m

N:C ratio: Decreased

Nucleus: Segmented, with

two to five lobes connected

by thin filament

Chromatin: condensed, stain deep

purple blackCytoplasm: Pink

Granules: Mainly small pinkish red

specific granules


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Maturation of Eosinophils

Morphological maturation of eosinophils is similar

to that of neutrophils.

Only at the myelocyte stage can the cell be

identified as an immature eosinophil.

Eosinophilic myelocyte contain large, eosin-

staining granules.

Maturation from myelocyte to the metamyelocyte,

band, and segmented eosinophil stage is similarto

neutrophils.


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Characteristics of Eosinophils

Size: 12 to 15 m

Nucleus: No more than 2-3

lobes.

Chromatin: Stain dark purple

Cytoplasm: Orange red

Granules:Abundant with large

acidophilic (Eosin-loving) granules.


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Maturation of Basophils

Morphological maturation of basophils is similar

to that described for neutrophils.

First recognizable stage is promyelocyte:

basophilic promyelocyte is smaller, with higher

N:C ratio than that of neutrophil or eosinophil

Basophilic promyelocyte contain large purple

black granules.

Maturation from promyelocyte to the

metamyelocyte, band, and segmented basophile

stage is similarto neutrophils.


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Basophilic granules contain

heparin and histamine.

Mast cells have granules that

have an enzyme content

similar to those of the blood

basophil.


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Size: 10 to 15 mNucleus: Segmented

Chromatin: Stain dark

purple

Granules: Many purple

in color, obscuring

the background of

the cytoplasm

Characteristics of Basophils


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Myeloblast: High N/C ratio. Cytoplasm is agranular. Nucleus has a fine

chromatin pattern


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Promyelocyte: Cytoplasm contains nucleus with a fine chromatin pattern and

nucleoli. Numerous primary azurophilic granules.


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Myelocyte: Cytoplasm is pinkish blue, indicating secondary granuleformation.

Nucleus is oval and eccentric with a moderately clumped chromatin pattern.


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Metamyelocyte: Cytoplasm contains a few azurophilic primary granules but

mostly pinkish-blue secondary granules. Nucleus indented with dense chromatin

clumping.


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Neutrophilic Band: Cytoplasm is pinkish-blue due to secondary granules. Nucleus is

clumped, and has a horseshoe shape that has uniform width throughout the nucleus.


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Segmented Neutrophil: Cytoplasm is finely granulated. Nucleus is segmented.


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Eosinophilic Myelocyte: Cytoplasm contains numerous red-orange granules and few

dark azurophilic granules. Nucleus is oval and eccentric.


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Basophilic Myelocyte: Cytoplasm has smaller black granules that are more intense on

the right of the nucleus. Nucleus is oval with moderately clumped chromatin.


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Basophil:Cytoplasm contains numerouslarge black granules thatobscure the nucleus.


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Hem II Chapter 14 Part 1 2016